The U.S. Department of Energy's Thomas Jefferson National Accelerator Facility

Protons and Neutrons Get Social in the Nucleus

At Jefferson Lab, scientists bombard nuclei with electrons in experiments to probe protons and neutrons – collectively called nucleons – and how they combine to form the nucleus of an atom. Data from these experiments are then compared to theoretical models. The models are based on theoretical insights into the nature of nuclear interactions and on inputs from decades of experiments. Many of these calculations are computationally intensive, and require the use of a big computer, such as the world's fifth-most-powerful computer, Argonne National Laboratory's IBM BlueGene/Q (Mira). Image courtesy of Argonne National Laboratory

When you post a joke, picture or link on Facebook, you have the option of sharing not only with your friends, but also with their friends, or "friends of friends." It turns out that something similar occurs inside the nucleus of the atom.

A new, robust calculation shows that "friends of friends" sharing by protons and neutrons in the carbon nucleus plays a significant role in its structure. Carbon is an essential ingredient for all life on Earth, as well as the sixth most abundant element in the universe. Its nuclei are among the most popular with physicists, who are studying them to unlock the secrets of the sub-atomic world.

At Jefferson Lab, scientists bombard carbon nuclei with electrons in experiments to probe protons and neutrons and how they combine to form the nucleus. The data from these experiments are then compared to theoretical models that have been developed by theorists. The models are based on theoretical insights into the nature of nuclear interactions and on inputs from decades of experiments on proton and neutrons – collectively called nucleons – and how they interact........ more

Physicworld.com, the Institute of Physics magazine, posted an article on preliminary results announced on an experiment conducted at Jefferson Lab. The Sept. 16 article was titled “Experiment probes strength of the weak interaction”..... more

Yaroslav Derbenev, a senior staff scientist with Jefferson Lab’s Center for Advanced Studies of Accelerators (CASA), was among the group of researchers to receive an inaugural Dieter Möhl Award....... more

The last piece of a huge, $2 million drift chamber built by Old Dominion University physicists and technical staff has been delivered to Jefferson Lab. The drift chamber will be assembled with other sections as part of CLAS 12..... more

Protons and Neutrons Get Social in the Nucleus

Pictured is the world's fifth-most-powerful computer, Argonne National Laboratory's IBM BlueGene/Q (Mira). The computer was used by Jefferson Lab scientists and their colleagues to carry out computationally intensive calculations that helped them better understand the nucleus of carbon atoms. Image courtesy of Argonne National Laboratory

When you post a joke, picture or link on Facebook, you have the option of sharing not only with your friends, but also with their friends, or "friends of friends." It turns out that something similar occurs inside the nucleus of the atom.

A new, robust calculation shows that "friends of friends" sharing by protons and neutrons in the carbon nucleus plays a significant role in its structure. Carbon is an essential ingredient for all life on Earth, as well as the sixth most abundant element in the universe. Its nuclei are among the most popular with physicists, who are studying them to unlock the secrets of the sub-atomic world.

At Jefferson Lab, scientists bombard carbon nuclei with electrons in experiments to probe protons and neutrons and how they combine to form the nucleus. The data from these experiments are then compared to theoretical models that have been developed by theorists. The models are based on theoretical insights into the nature of nuclear interactions and on inputs from decades of experiments on proton and neutrons – collectively called nucleons – and how they interact.

With six protons and six neutrons, the carbon-12 nucleus has recently become something of a Goldilocks nucleus for physicists to study. It's neither so small that its structure fits neatly into the theoretical models of how nuclei are put together, nor so large that more complicated models for describing its structure are too complex to calculate.

In calculating the structure of the carbon nucleus, one of the things that theorists were really trying to calculate is the so-called binding energy. The binding energy is a measure of how strongly the nucleons are interacting. It's generated by the forces that hold the nucleons together.

In the past, theorists were only capable of calculating the binding energy of carbon by simplifying their calculations somewhat. For instance, they'd limit the calculations related to how a single nucleon in a nucleus interacts with a so-called mean field generated by all the other nucleons, in a type of model called a shell model. But in the carbon nucleus, tightly packed with 12 nucleons, such calculations simply don't describe the nucleus very well.

"As a matter of fact, if you want to reproduce the empirical binding energy of a nucleus, you need two-nucleon and three-nucleon interactions. With just two nucleon potentials only, you get less binding than is observed," Schiavilla explains.

The new calculation is the first to take into account a nucleon's interactions with multiple other nucleons in the nucleus at a time – a concept that can be thought of as "friends of friends" sharing. When compared to the actual binding energy of carbon-12, which has been experimentally measured, the new calculation was spot on.

"It turns out, these two- and three-body forces reproduce very well the binding energy of carbon-12, and in fact, all nuclei in between, from helium-3 to boron-10," Schiavilla says.

Another aspect of the new calculation involves how the nucleus responds to electromagnetic fields. As mentioned earlier, Jefferson Lab uses its Continuous Electron Beam Accelerator Facility to hurl electrons at atomic nuclei. Most of the electrons will pass on through the atom, completely missing the nucleus at its heart. But sometimes, the electrons will come close enough to the positively charged nucleus to interact with it via the electromagnetic force.

These experiments can have two outcomes: either they leave the nucleus intact, yielding the nucleus' form factor, which is related to its size and the distribution of the protons inside it; or they smash the nucleus into pieces, yielding a measurement of its "inelastic response."

The theorists found that for these quantities, too, "friends of friends" sharing was a very important factor. They found that while the electron probe often interacts with just one nucleon in the nucleus, it can also interact with multiple nucleons.

Or, as Schiavilla puts it, "If you want to describe in a quantitative way the response of a nucleus to electromagnetic probes, you need to include not just the coupling of this probe to single nucleons, but also to pairs of nucleons."

In fact, the "friends of friends" sharing aspect of the calculation accounted for as much as half of the inelastic response. And, for the first time, the total response that was calculated by the theorists matched that obtained in experiments.

"It gives us the confidence that we have an understanding of the structure of carbon-12 and of the dynamics of the nucleons inside it," he says.

Now, Schiavilla and his colleagues have turned their attention to other facets of their calculations. It turns out that the calculation may clear up a mystery in another realm of subatomic physics. Neutrinos are ghostly particles that are produced as a byproduct of the nuclear fusion that powers the sun. They are ghostly particles that can float through stars and planets relatively unhindered. Experimenters studying neutrinos directed a beam of the particles at carbon nuclei. The result had seemed to indicate that the carbon nucleus was more responsive to neutrinos than theorists' calculations predicted.

According to Schiavilla, once this new calculation is taken into account, that discrepancy might largely disappear. He and his colleagues will soon complete a study of the response of the carbon-12 nucleus to the weak force, its so-called weak interaction, which is being probed in the aforementioned neutrino experiment.

Editor’s note: This article was first published in the Sept. 16, 2013 issue of DOE Pulse. For this and other articles about research and advancements at the DOE national labs, visit the DOE Pulse web site at: http://web.ornl.gov/info/news/pulse/no397/

Jefferson Lab News Tracker:
Early Results from Q-weak Experiment Published

Q-weak, a large-installation experiment conducted using CEBAF, measured the proton’s weak charge. Pictured here is part of the experimental assembly during installation in Hall C.

Physicworld.com, the Institute of Physics magazine, posted an article on preliminary results announced on an experiment conducted at Jefferson Lab. The Sept. 16 article was titled “Experiment probes strength of the weak interaction” and was written by Jon Cartwright, a freelance journalist based in Bristol, UK.

The large-installation experiment, designed to determine the weak charge of the proton, was carried out in Jefferson Lab’s Experimental Hall C.

Lab Scientist Among Recipients of Inaugural Dieter Möhl Award

The inaugural presentations of the Dieter Möhl Award were made at the COOL ’13 Workshop. The awards were presented by Möhl’s wife, Lisa Moehl. Here she presents the award medal to Jefferson Lab’s Yaroslav Derbenev (center). Also pictured are (left to right): Gerard Tranquille, CERN, chair of the workshop; and fellow award recipients (background) Vasiliy Parkhomchuck, BINP, Novosibirsk; and Igor Meshkov JINR.

Yaroslav Derbenev, a senior staff scientist with Jefferson Lab’s Center for Advanced Studies of Accelerators (CASA), was among the group of researchers to receive an inaugural Dieter Möhl Award.

Derbenev and fellow recipients accepted their awards during a ceremony on June 14 in Murren, Switzerland, at the COOL ‘13 Workshop.

Derbenev was recognized for a number of groundbreaking contributions he has made to beam cooling in particle accelerators.

“Over his career, Slava has made several important and original contributions to the field of beam cooling,” said Yuhong Zhang, a CASA colleague who attended COOL ‘13. “Slava contributed to the development of the theoretical foundation of conventional electron cooling. He co-discovered magnetized electron cooling, proposed a novel stochastic cooling concept (now called coherent electron cooling) using beam instability as a signal amplifier, and most recently, he proposed six-dimensional muon cooling with a helical dipole channel.

“His idea forms the basis for cooling the Jefferson Lab Medium-Energy Electron-Ion Collider (MEIC) being proposed, and is also the concept used for the coherent electron cooling design for the eRHIC, Brookhaven National Lab’s proposed electron-ion collider,” Zhang added.

"Yaroslav has done groundbreaking work and his efforts and advancements in the field of beam cooling are invaluable for Jefferson Lab and research facilities around the world. I am delighted that he and his colleagues – many who personally worked with Dieter years ago – were recognized with this new award,” said Andrew Hutton, associate director of Jefferson Lab’s Accelerator Division.

Award Honors Work and Legacy of Pioneer in Field of Beam Cooling

The Dieter Möhl Award was created in honor of the many contributions made by Dieter Möhl, (1936-2012) an internationally recognized physicist and leader in the field of beam cooling in particle accelerators. He worked for many years at CERN and was among the pioneers who first demonstrated the viability of stochastic cooling.

According to the CERN Courier, “his theoretical work was unique in terms of the understanding, improvement and extension of beam-cooling techniques to many accelerators and storage rings.”

The award was created and funded by Möhl’s family. According to the international program committee of the COOL workshop, the award recognizes researchers who have made important and original contributions in the field of beam cooling in particle accelerators during their careers, and provided continuous support of the COOL workshop series.

“Dieter was a great scientist and a wonderful human being,” said Hutton. “It is heartwarming to see his work and his legacy remembered with this award.”

The COOL international workshops, where the awards were presented, focus on particle beam cooling, beam cooling systems and related topics – ranging from state-of-the-art beam cooling systems (including electron, stochastic, laser and ionization cooling) for the applications of beam cooling traps, and heavy ion, muons and anti-proton beams. Discussions focus on new developments and techniques and the status of existing and future facilities. The workshop is held in every other year; the next one, COOL ‘15, will be held at Jefferson Lab with Derbenev and Zhang as the workshop co-chairs.

ODU Delivers Last Drift Chamber Section is Built for Lab’s Upgrade Effort

Old Dominion University scientists, technicians and students have completed building a set of detector assemblies that are part of Jefferson Lab’s 12 GeV Upgrade project. The drift chamber assemblies seen in these photos will become part of CLAS 12 (the CEBAF Large Acceptance Spectrometer) that will be installed in Hall B. These photos were taken during the summer of 2012 in the ODU Nuclear and Particle Physics High Bay Laboratory clean room.

The last piece of a huge, $2 million drift chamber built by Old Dominion University physicists and technical staff has been delivered to Jefferson Lab. The drift chamber will be assembled with other sections as part of CLAS 12 (the CEBAF Large Acceptance Spectrometer 12 detector system) and installed in Hall B as part of the 12 GeV Upgrade to the Continuous Electron Beam Accelerator Facility.

The triangle-shaped component – you might think of it as a one-ton harp – is strung with 5,000 highly sensitive wires and required a special "air cushion" ride to Newport News. It arrived at the lab on Sept. 19. Four other components like it were shipped from ODU over the past 18 months.

"It's a great feeling," Project Leader Lawrence Weinstein, an ODU professor of physics who has been a lead investigator for experiments at Jefferson Lab, said in a news release posted on the ODU website. "We succeeded again, on time and under budget."

His reference to "again" was to note that he and other ODU physicists built one of the first drift chambers that was installed at Jefferson Lab about two decades ago.

Below the Fold:

Lab Kicks off United Way Campaign with Picnic on Oct. 2

There are many signs that autumn has arrived, the nights get longer, the days get shorter and the United Way fundraising campaign gets underway at Jefferson Lab. This year’s drive starts on Wednesday, Oct. 2, with the now traditional kick-off picnic and raffle.

“The United Way and United Way-supported charities do much to bolster this community and to help individuals dealing with a variety of difficult situations,” points out Chief Operating Officer, Mike Dallas. “A pledge or donation through the United Way is a great way to give back to our community, to help make our community a better place and to say ‘thank you’ for the support this region has given to the lab over the years.”

The United Way of the Virginia Peninsula partners with local businesses, municipalities, individuals and other non-profits in a community-wide fundraising campaign that provides necessary resources to programs that address a broad range of community needs. Donations and pledges help fund programs that target everything from basic needs like food and shelter, to crisis and emergency response, after-school programs, affordable daycare, transportation for the elderly, job training for the disabled and much more.

Donation/pledge forms will be available beginning on Oct. 1 at the reception desks at the Support Service Center, Bldg. 28, and CEBAF Center, Bldg. 12, and may be picked up at the United Way Raffle ticket sales table in the CEBAF Center lobby daily during lunch time starting on Oct. 2. The United Way form is also available here in pdf format. Send or deliver your completed form to Joshua Cameron, Human Resources, in CEBAF Center, Room B214, Mail Stop 12-B, by Friday, Nov. 1. Direct questions to Cameron at jcameron@jlab.org or ext. 7628.
The kick-off picnic will take place from 11:30 a.m.–1:30 p.m., on Oct. 2 in CEBAF Center. All members of the lab community are invited to participate. All picnic food and beverage items will be $1 each; and the menu will include hot dogs, hamburgers, veggie burgers, assorted chips, assorted canned soda and bottled water. Additional food and beverage items may be purchased in the cafeteria.
Raffle tickets for three iPad minis will go on sale at that time and will run through Oct. 29. Tickets will be available for $1 each and may be purchased at a table to be set up in the CEBAF Center lobby from 12–1 p.m. on workdays.
The winning ticket for each iPad mini will be drawn during the Jefferson Lab Activities Group Tailgate picnic on Oct. 29. Winners need not be present to claim their prize, but must do so by 5 p.m. Monday, Nov. 4. One iPad win per person.

Eurest's Quark Cafe staff will donate the food for the event, and handle all the food preparation and presentation. Members of lab management plan to serve the food.

All proceeds from the picnic and the raffle go to the United Way of the Virginia Peninsula to support community services programs.

"The United Way is an important community support system. Please give generously; there are many people in the area who are greatly helped by agencies supported through the United Way," Dallas concluded. "Thank you for your support."

Doctoral Student Works to Advance Lower-Cost SRF Capability

Feisi He stands next to the specially sized die required for the fabrication of the R&D cavities he worked on while at Jefferson Lab. Here he holds one of the prototype aluminum bowls (one-half of a cavity cell).

Born in southern China, Feisi He (pronounced face her) moved to Beijing with his parents when he was three. Growing up in that bustling city, he was surrounded at home by literature and literary pursuits – since his parents both worked in the world of publishing – his dad as a chief editor at a magazine and his mom in accounting for a publishing company.

Science came easy to him as a youngster, he recalls, although his chosen path was not immediately clear.

“I was first interested in energy,” he adds. “I was always dreaming of doing work related to that, but I didn’t know what it would be.”

When He entered Peking University in 2003, he was still undecided, but that ended after friends suggested that he pursue physics and he visited the accelerator group at the university.

“I saw right away that the people there were so excited with the work they were doing! That made my decision – to go into that,” he noted.

Upon graduating in 2007 with a bachelor’s degree in physics, he went directly into the university’s Ph.D. program, where he is focusing on superconducting radiofrequency (SRF) technology. He received a scholarship in the 2008-09 academic year, and published several papers as first author, including “Design of a capacitive main power coupler for RF superconducting accelerators,” which appeared in Chinese Physics; “Analytical and Experimental Study of Crosstalk in the Superconducting Cavity,” which he presented at the PAC09 conference; “Manufacturing of the main accelerator with TESLA-like 9-cell SRF cavity at Peking University” for IPAC10, and “Some Design Analysis on the Low-Beta Multi-Spoke Cavities” for SRF2011.

By the beginning of 2011, while in the fourth year of his doctoral program, He and his adviser, Professor Kui Zhao, decided it was time for him to search for additional challenges. He came to Jefferson Lab in February 2011 as a joint Ph.D. student, and has been working with Haipeng Wang, and Robert Rimmer.

He admits to having no preconceived notions of what the United States would be like before arriving, and so had few surprises, although He notes that Newport News is far quieter than Beijing.

Since late 2011, he has been involved in a Department of Energy project that aims to prove an SRF technology for an affordable, high intensity X-ray light source for an accelerator that would run at 4K (Kelvin) with an easy-to-maintain cryomodule for use at universities, hospitals and other smaller institutions. The technology, if successful, would be adopted by MIT. The single-cell elliptical cavity (that will serve as the test bed for many new ideas) is 1.6 times larger than a CEBAF single cell.

The initial fabrication, which was made out of aluminum, required totally new, larger dies in order to force the material into shape. Work that normally took a skilled technician half an hour took an entire week. New methods of tooling in order to do the trim work were required, and new approaches for the cleaning had to be undertaken because the cavity sections didn’t fit in either the ultrasonic tank or the fume hood.

”We would usually immerse it upside down during degreasing and weld-preparation cleaning, but it didn’t fit,” he explained. “We had to figure out a way to get it in at an angle.” One low-temperature test was finished in early September to establish a performance baseline with post processing of buffered chemical etching, higher pressure rinsing and clean room assembly. More efforts are on the way to improve the cavity performance with various treatments.

He pointed out that one major objective – production – has been achieved. ”The good news,” he said with a smile, “is that now we have all the tools to do this size again.”

The team of JLab scientists, engineers and technicians working on the project were pressing against a Sept. 21 deadline, to present their work at the SRF 2013 workshop in Paris. He will return to China immediately thereafter, and expects to complete his Ph.D. at the end of the year.

Lab Announces Fall Science Series Lectures on Oct. 15 and Nov. 12

As of Oct. 7, the Jefferson Lab Science Series lecture scheduled for 7 p.m. on Oct. 15 has been cancelled.

Jefferson Lab will host two Fall Science Series Lectures this season. The first is set for Tuesday, Oct. 15 and will feature a Jefferson Lab scientist discussing the exploration of dark matter using accelerators like those at Jefferson Lab. Then on Nov. 12, an astronomer from the University of Virginia will discuss the beginnings of our universe.

On Oct. 15, Michelle Shinn, chief optics scientist for Jefferson Lab’s Free-Electron Laser (FEL), will present “Exploring the Nature of Matter Along the High-Intensity Frontier.” Her talk will address how accelerator-based experiments, using machines like the Continuous Electron Beam Accelerator Facility (CEBAF) and the FEL, could be used to find particles responsible for the effects scientists attribute to dark matter.

“There are a number of hypothesized Beyond Standard Model particles with masses that put them in the range of accelerators doing medium-energy physics,” she explains. Her presentation will introduce the concept of superconducting radiofrequency (SRF) acceleration, specifically as it is used at Jefferson Lab, to produce beams of particles with high (many 10’s to 100’s of MHz) repetition rate. These properties of the electron accelerators at Jefferson Lab and the three – and soon to be four – experimental halls provide an ideal platform for conducting these experiments at the Intensity Frontier, according to Shinn.

She will then discuss experiments being planned and proposed that will attempt to detect two classes of particles.

“Throughout history and across all cultures, humans have wondered how their World came into being,” Whittle observes. “In the past few decades the fields of cosmology and its parent subject astronomy have made enormous strides in answering that question.”

His talk will review the multiple lines of evidence that indicate that the universe was born in a "Big Bang" – an exceedingly hot, dense expanding fireball of gas and light. “Today, the story of the birth of the universe can be told with considerable detail and confidence,” Whittle says, “and is a story as rich and inspiring as we could have hoped for.”

Both lectures are free and open to students and adults. Both lectures will begin at 7 p.m., in the CEBAF Center auditorium located at 12000 Jefferson Ave, Newport News, and will last about an hour. Seating in the auditorium and overflow area is available on a first-come, first-served basis and is limited to about 300 people. People arriving once capacity has been reached will be turned away.

All those under age 16 must be accompanied by a parent or responsible adult. Everyone over 16 is asked to carry a valid photo ID. Security guards may perform ID, parcel and vehicle checks.

Volunteers Needed to Help with BEAMS - Lab's Science and Math Outreach Program

BEAMS students learn about energy transfer, insulators and scientific procedure during the "Cold Stuff" activity. Jefferson Lab volunteers are needed to help the students with a range of classroom activities and as mentors for Role Model visits.

Becoming Enthusiastic About Math and Science – or BEAMS – Jefferson Lab's long-running math and science enrichment program for middle school students needs your help. Lab staff members, users and students interested in assisting with educational activities conducted at the lab during normal business hours, are encouraged to contact Christine Wheeler, Science Education.

BEAMS supports Newport News inner-city public school students as they progress from fifth through eighth grade. Nearly 1,500 students and their teachers visit Jefferson Lab between two and five days each school year to participate in BEAMS science and math activities conducted by scientists, engineers, technicians and administrators.

Volunteers spend about 75 minutes in a BEAMS classroom on the lab campus either leading an educational activity or assisting students as they carry out an activity.

Volunteers are also needed to serve as role models for the students. A Role Model volunteer visits with students for 15 minutes and shares information about their career at the lab. The visits may take place in the volunteer's office or other appropriate work area. Role Model visits are scheduled throughout the school year – so volunteers can pick the time of year that works best for them.

For the 2013-2014 academic year, BEAMS class visits will begin in late September and run through May 2014. Usually two classes attend at a time and participate in two to four separate activities during each day-long visit.

"JLab staff, students and users are critical to the success of the lab's science education programs, especially BEAMS," Wheeler says. "Our BEAMS volunteers have been sharing their passion and excitement for math, science and technology with students for more than 20 years. Students gain knowledge and skills and volunteers have a chance to make a difference in the lives of students and have fun working with lots of smiling faces. Everybody wins!

"Want to help, but not sure how? That's what we're here for," Wheeler points out. "Science Education staff members are happy to provide the training you need whether you’ve assisted previously or you are volunteering for the first time. If you want to observe a classroom activity before signing up to volunteer, we can schedule that, too."

BEAMS program goals include: motivating students to boost their learning; strengthening students' math and science skills with hands-on activities; and having students interact with individuals who use math and/or science in their daily work environment. BEAMS also provides teachers with classroom activities based on JLab science and technology.

M. Shinn on Temporary DOE Assignment

Michelle Shinn, Free-Electron Laser Division chief optics scientist, is on a year-long temporary work assignment with the U.S. Department of Energy.

Michelle Shinn, Free-Electron Laser Division chief optics scientist, has started a year-long temporary work assignment (aka detail) with the Office of Nuclear Physics, Facilities and Project Management Division at the Department of Energy offices in Germantown, Md.

Shinn is delighted to be a DOE detailee and is looking forward to learning more about the DOE through her daily interactions with the Office of Nuclear Physics staff, staff in other DOE offices, and researchers at other laboratories and facilities.

“I was so excited to be offered this opportunity,” she said as she finished up some work at the lab before beginning her new assignment on Aug. 5. “It is all exciting with so much to learn; and it should be a wonderful opportunity for networking and gaining a better understanding of DOE and the national lab system.”

Lab Community Mourns Death of Carl Iannacone

Carl J. Iannacone

Jefferson Lab Property Manager, Carl J. Iannacone, 61, died Sept. 2 at his home. He had been with the lab since August 2010.

Iannacone was born in St. Petersburg, Fla., and graduated from the University of Arkansas at Little Rock with a master’s degree in public administration. Before coming to Jefferson Lab, he had worked at the University Hospital of Arkansas. In addition, he was an active member of the National Property Management Association (NPMA). He was a past president of the organization, had held several other leadership positions within the NPMA, and had served more than 10 years on its executive board.

He loved bowling with friends on Wednesday evenings at Village Lanes Bowling Alley in Gloucester, and was an avid reader. He enjoyed baseball and watching the Atlanta Braves.